(1) Field of the Invention
This invention relates to a technology for making smaller and lighter RF passive circuits and RF amplifiers equipped with via-holes.
(2) Prior Art
Recently, various types of mobile communication tools, such as portable phones or portable information terminals have been commercialized all over the world. As portable phones, cellular phones for bands of 900 MHz and 1.5 GHz, and Personal Handyphone System (PHS) for a band of 1.9 GHz are two examples that are commercialized in Japanese market. Other examples include world-famous GSM, and CDMA among the technologies adopted in PCS (Personal Communications Services) in the U.S.A.
As a third-generation mode following the analogue mode and the digital mode, IMT2000 is planned to be commercialized in the future.
In developing mobile communication terminals especially portable terminals, it is an inevitable trend to seek smaller and lighter terminals. Accordingly, it is important to achieve a technology for making smaller and lighter components for these terminals.
As a trend, it is desired to make high frequency components of the portable terminals as a monolithic microwave IC (MMIC). The MMIC, in which active elements, their matching circuits, and bias circuits are integrated on the same substrate, is more advantageous in making smaller products than a Hybrid IC which is structured to have circuits and bias electricity-feeding circuits as outside-chips.
Even using the MMIC, it is required to ground circuit elements. Conventional grounding methods include a method of wire-bonding from the surface of semiconductor substrates, and a via-hole method. It is more effective to use the via-hole method in achieving high-quality and low cost for packaging, which makes the via-hole method more frequently adopted in the MMIC.
The following is a description of an example of a conventional type of RF passive circuit and RF amplifier equipped with via-holes with reference to FIGS. 8A-8D.
FIG. 8A is a schematic circuit diagram of a conventional RF amplifier which includes RF passive circuits equipped with via-holes, and FIGS. 8B and 8C are pattern diagrams of conventional RF passive circuits both equipped with a via-hole.
As FIG. 8A shows, a source-ground type of RF amplifier is constructed by connecting: a gate bias resistance 805 and an input matching circuit 806 to a gate terminal 802; a drain voltage feeding circuit 807 and an output matching circuit 808 to a drain terminal 803; and a source terminal 804 to a ground terminal 809, in the field effective transistor (FET) 801. An input terminal 810 and an output terminal 811 are both 50 xcexa9 impedance, and the input matching circuit 806 and the output matching circuit 808 are adjusted to 50 xcexa9. Further, each of an input DC cut capacitor 812 and an output DC cut capacitor 813 is inserted to the input side and the output side respectively.
The input matching circuit 806 consists of an input matching parallel inductor 814, an input matching parallel capacitor 815, and an input matching serial inductor 816. The input matching parallel capacitor 815 is grounded by an input matching circuit via-hole 821.
The output matching circuit 808 consists of an output matching serial inductor 817, and an output matching parallel capacitor 818. The output matching parallel capacitor 818 is grounded by an output matching circuit via-hole 822.
The drain voltage feeding circuit 807 consists of a choke inductor 819 and a bypass capacitor 820. The bypass capacitor 820 is grounded by a drain voltage feeding circuit via-hole 823.
FIGS. 8B and 8C are both pattern diagrams of an RF passive circuit with a via-hole; each of them shows the input matching circuit 806 and the drain voltage feeding circuit 807 respectively. FIG. 8D shows a cross-sectional view taken along line (A-Axe2x80x2) of FIG. 8B. The following is a description of a common part between the input matching circuit 806 and the drain voltage feeding circuit 807, taking an example of the input matching circuit 806.
Constituting elements of the aforementioned input matching circuit 806 is made, as a semiconductor substrate, on a surface of a GaAs substrate 824. Both of the input matching parallel inductor 814 and the input matching serial inductor 816 are made in a spiral-electrode-pattern, and the input matching parallel capacitor 815 is made in an MIM(Metal-Insulator-Metal) capacitor pattern.
As FIG. 8D shows, the spiral-electrode-pattern is made on the GaAs substrate 824 which is covered by an insulator film 834 such as silicon oxide. Specifically, the spiral-electrode-pattern is a structure where a lower wiring metal layer 831 which is made by gold/titanium vacuum evaporation is connected to an upper wiring metal layer 830 made by gold-plating by means of a contact hole 833, with a between-layer insulator film 832 in between.
On the other hand, the MIM capacitor is a structure where an upper wiring metal 829 is formed on a dielectric layer 828 under which is an electrode extended from the lower wiring metal layer 831; the upper wiring metal 829 is made by gold/titanium vacuum evaporation and the dielectric layer 828 is titanium oxide strontium (SrTiO3:STO) with a permittivity of 100 or more. The end of the electrode extended from the upper wiring metal 829 is connected to a ground metal layer 826 which is situated on the via-hole, as FIGS. 8B and 8C show.
The input matching circuit via-hole 821 can be formed by etching from the main surface of the GaAs substrate 824 where circuit elements were made (a surface via-hole). Or, it could also be formed by etching from the other main surface (a backside via-hole). Inside the via-hole 821, an electric conducting film is conducted to a backside ground metal 829. This electric conducting film is electrically connected to the upper wiring metal 829 of the MIM capacitor through the ground metal layer 826.
Further, as depicted in FIG. 8C, constituting elements of the drain voltage feeding circuit 807 are formed, as a semiconductor substrate, on the surface of the GaAs substrate 824. As for the choke inductor 819, a spiral-electrode-pattern is used, and as for the drain voltage feeding circuit via-hole 823, either a surface via-hole or a backside via-hole is used for forming.
Note that a feeding terminal 825 is structured by extending a drain voltage terminal 836 from the lower wiring metal layer 831 through an extending wire 835.
Thus structured as above, the following constituting elements of the RF passive circuit are formed on and through the GaAs substrate: the spiral inductor, the MIM capacitor, and the via-hole. Moreover, as FIG. 8C shows, the above three elements are positioned at a different location two-dimentionally, and are connected to each other by wiring. The elements constitute the RF amplifier with a help of the input matching circuit 808 and the drain voltage feeding circuit 807.
As seen above, the conventional type of RF amplifiers and RF passive circuits cannot be made smaller in size, due to the two-dimensional positioning of the constituting elements of the drain voltage feeding circuit 807, which inherently take much space.
Based on the stated problem, the object of the present invention is to realize smaller RF passive circuits and RF amplifiers equipped with via-holes.
To achieve the above object, the present invention is characterized by a structure of being equipped with a spiral inductor formed on a main surface of a semiconductor substrate, and a via-hole made from the main surface and through the semiconductor substrate. The via-hole is made at the position adjacent to the spiral inductor, with a dielectric layer and a wiring metal layer formed on a metal film of the via-hole so as to hold a capacity element between the metal film and the wiring metal layer, and the spiral inductor extends at one end to be electrically connected with the wiring metal layer.
The above structure enables to incorporate a capacitor in a via-hole, thereby enabling a three-dimensional location of the following three elements on one semiconductor substrate; a spiral inductor, a capacitor, and a via-hole. Thus reduced occupancy will produce an effect of enabling a smaller RF passive circuit and an RF amplifier made of the RF passive circuits as main components.
Furthermore, the RF amplifier of the present invention is characterized by a structure of utilizing the RF passive circuit equipped with the via-hole as a matching circuit, or as an RF choke in a bias feeding circuit.
Furthermore, an RF passive circuit of the present invention is equipped with a spiral inductor formed on a main surface of a semiconductor substrate and a via-hole that is made from the main surface and goes through the semiconductor substrate. The via-hole is placed adjacent to the spiral inductor, and on a metal film of the via-hole, a first dielectric layer, a first wiring metal layer, a second dielectric layer, and a second wiring metal layer are formed in this order, so as to form a first capacity element between the metal film of the via-hole and the first wiring metal layer, and a second capacity element between the first wiring metal layer and the second wiring metal layer. The present invention is further structured to have the metal film and the second wiring metal layer electrically connected so as to hold a static capacity determined by a sum of the first capacity element and the second capacity element. The present invention is further characterized by a spiral inductor extending at one end to be electrically connected to the first wiring metal layer.
This structure will help to make a smaller RF passive circuit and a smaller RF amplifier by enabling a three-dimensional location of a spiral inductor, a capacitor, and a via-hole. Moreover, a static capacity will be increased without increasing the occupancy, which will facilitate designing of such a circuit as a bias feeding circuit of an RF amplifier which inherently requires large capacity.
In addition, the RF amplifier of the present invention is characterized by utilizing the RF passive circuit equipped with a via-hole as a matching circuit, or as an RF choke of a bias feeding circuit.
Moreover, the RF passive circuit equipped with a via-hole is characterized by a metal film of the via-hole provided through a main surface of a semiconductor substrate which further extends along the main surface, and by a spiral metal layer formed on the extended part of the metal film, which works as an inductor with a dielectric layer in between. Here, the extended part of the metal film can be made in the same spiral pattern as the spiral inductor which is formed on the metal film.
The above structure enables to accommodate a static capacity where the extended part of the metal layer and the spiral metal layer face each other with a dielectric layer in between. This realizes a three-dimensional location of a spiral inductor, a capacitor, and a via-hole, thereby reducing the occupancy thereof. This also helps to make a smaller RF passive circuit, and a smaller RF amplifier.
Moreover, the RF amplifier of the present invention is characterized by utilizing the RF passive circuit equipped with a via-hole as a matching circuit, or as an RF choke of a bias feeding circuit.
In addition, the RF passive circuit equipped with a via-hole that the present invention is applied to, is characterized by making a via-hole that goes through a semiconductor substrate, and by making a dielectric layer so as to cover a metal film of the via-hole which is provided through a main surface of the semiconductor substrate, and by an inductor formed as a spiral metal layer which covers the dielectric layer so as to face against the metal film at one part, where a capacity element is held between the via-hole and the inductor.
The above structure enables a three dimensional location of a spiral inductor, a capacitor, and a via-hole from inside to the surface of the semiconductor substrate, thereby reducing the occupancy thereof, and helps to make a smaller RF passive circuit and a smaller RF amplifier.
In addition, the RF amplifier of the present invention is characterized by utilizing an RF passive circuit equipped with a via-hole as a matching circuit, or as an RF choke of a bias feeding circuit.
Moreover, the RF passive circuit with a via-hole that the present invention is applied to, is characterized by being equipped with a via-hole that goes through a semiconductor substrate from the other main surface of the semiconductor substrate, and by having a dielectric layer on a metal film of a via-hole provided through the main surface of a semiconductor substrate, and having a metal layer on the dielectric layer, and holding a capacity element between the metal film of the via-hole and the metal layer.
The above structure realizes a three dimensional location of a capacitor and a via-hole on one semiconductor substrate, thereby reducing the occupancy thereof. This realizes a smaller RF passive circuit and a smaller RF amplifier.
In addition, the RE amplifier of the present invention is characterized by electrically connecting a wiring metal layer of the RE passive circuit with a gate terminal of a common gate circuit of a EET, or with a base terminal of a common base circuit of a bipolar transistor, or by electrically connecting, with a source terminal of a FET, a terminal which is a terminal of a resistance element electrically connected to the metal layer, so as to form a self bias circuit.
In addition, the RF passive circuit of the present invention equipped with a via-hole is characterized by making a via-hole that goes through a semiconductor substrate, and by forming a dielectric layer and a wiring metal layer on a metal film of the via-hole, in this order, so as to hold a capacity element between a ground metal layer and the wiring metal layer.
The above structure enables a three dimensional location of a capacitor and a via-hole on one semiconductor substrate, thereby reducing the occupancy thereof. This helps making a smaller RF passive circuit and a smaller RF amplifier.
Moreover, the RF amplifier of the present invention is characterized by electrically connecting a wiring metal layer of the RF passive circuit with a gate terminal of a common gate circuit of a FET, or by electrically connecting the wiring metal layer with a base terminal of a common base circuit in a bipolar transistor, or by connecting a terminal of a resistance element of the RF passive circuit with the ground metal layer, and the other terminal to the wiring metal layer, so as to form a self bias circuit.
The RF passive circuit equipped with a via-hole that the present invention is applied to, is further characterized by making a via-hole that goes through a semiconductor substrate, and by forming, on a metal film of the via-hole, a first dielectric layer, a first wiring metal layer, a second dielectric layer, and a second wiring metal layer in this order. The RF passive circuit of the present invention is further characterized by having a first capacity element between the metal film and the first wiring metal layer, and the second capacity element between the first wiring metal layer and the second wiring metal layer, and by electrically connecting the metal film and the second wiring metal layer, so as to form a static capacity determined by a sum of the first capacity element and the second capacity element.
The RF amplifier of the present invention is further characterized by electrically connecting a first wiring metal layer of an RF passive circuit equipped with a via-hole with a gate terminal of a common gate circuit of a FET, or by electrically connecting a first wiring metal layer with a base terminal of a common base circuit of a bipolar transistor. Or the RF amplifier is characterized by electrically connecting one terminal of a resistance element with the metal film, and the other terminal with the first wiring metal layer, and the terminal of the resistance element which is electrically connected with the second wiring metal layer is further electrically connected with a source terminal of the FET so as to form a self bias circuit.